1. Field of the Invention
The present invention relates to a golf club head having a hollow shell made of metal, and particularly relates to a golf club head in which a shell made of metal is thin enough to be deformed easily at a time of hitting a ball, so that a repulsive property is superior, and a large carry can be obtained.
2. Description of the Related Art
Hollow golf club heads made of metal are used widely as wood type golf club heads such as drivers or fairway woods. Generally, as shown in FIG. 14, a hollow wood type golf club head 321 has a face portion 322 for hitting a ball, a crown portion 323 forming a top surface portion of the golf club head, a sole portion 324 forming a bottom surface portion of the golf club head, a side portion 325 forming the toe-side, rear-side and heel-side side surface portions of the golf club head, and a hosel portion 326. A shaft 327 is inserted into the hosel portion 326 of the golf club head 321, and fixed thereto by a bonding agent or the like. Incidentally, recently, a lot of golf clubs called utility clubs have come onto the market. As a kind of such utility golf club, various golf clubs each having a head resembling the above-mentioned wood type golf club head (that is, having a face portion, a sole portion, a side portion, a crown portion and a hosel portion) have also come onto the market.
As metal forming such a hollow golf club head, aluminum alloys, stainless steel, or titanium alloys are used. In recent years, titanium alloys are especially used widely.
In recent years, in order to increase a carry of a shot, there have been adopted various structures in which a face of a golf club head is thinned to make a face surface easy to be deformed elastically at a time of impact so as to increase the initial speed of a ball. However, there may be a case that the initial launch speed of the ball is not increased sufficiently only by the elastic deformation of the face surface.
Particularly, for an amateur golfer who has a low head speed, a sufficient launch angle cannot be obtained with a head deformable only in a face. In addition, since the spin quantity of a ball may be reduced, increase in the initial speed of the ball does not result in increase in the carry of the ball.
It is an object of the present invention to provide a golf club head in which elastic deformation is produced not only in a face surface but also in a crown portion at a time of impact of a golf ball. Accordingly, the initial speed of the ball can be increased while the launch angle and the spin quantity can be increased. Thus, even if a powerless golfer uses the golf club head, the golfer can obtain a sufficient increase of a carry.
According to the invention, there is provided a hollow golf club head made of metal comprising a front part having a face portion and a crown portion and made of a homogeneous material and a back part having a sole potion, a side portion, and hosel portion, wherein the front part and the back part are welded.
In such a golf club head, the constituent material of the front part may be made lower in Young""s modulus than the constituent material of the back part or a crown portion of the front part is formed to be thin. In this case, the front part as a whole can be made easy to be deformed elastically at a time of impact. Thus, at the time of impact, the elastic deformation is produced not only in the face surface but also in the crown portion. Accordingly, the initial speed of a ball can be increased while the launch angle and the spin quantity can be increased. Thus, even if a powerless golfer uses the golf club head, the golfer can obtain a sufficient increase of a carry.
According to the present invention, a center of the face portion may be the thickest portion of the face portion. In this case, the strength of the face portion center can be enhanced. When a peripheral area of the face surface is thinned, suitable deformation is produced in the face portion at the time of impact. Thus, the initial speed of the ball can be increased.
According to the present invention, the front part may include a highest portion of the crown portion, and the thickness of the highest portion and a neighbor area thereof may be made smaller than the thickness of a peripheral area of the neighbor area. In this case, the crown portion becomes easy to be deformed at the time of impact. Thus, the initial speed of the ball can be further increased.